In order to optimize technical parameters of a ball valve, such as diameter, pressure, torque, life, there are a variety of composite valve opening and closing mechanisms in recent years.
Chinese patent application No. 200720082066 disclosed a ball valve with low torque including a valve body, a valve ball, a valve seat, a supporting seat, a valve stem, a driving device and supporting connection member of valve ball. Disadvantageous of this ball valve is that the driving device has complex structures, which occupy much of the outer space of the valve. The driving device involves many components and the assembling process is complicated. The rotating angle for opening and closing of the valve is 180 degree. The workspace formed by the stem and the driving device will impose high requirements on sealing process. The traditional sealing means and process are likely to cause leakage. In addition, the processing costs are high, not suitable for environmental conservation purposes.
Recently, a guiding groove lifting ball valve was developed in domestic and overseas, which has an s-shaped guiding groove on a valve stem for engaging with the guiding pin so that the ball counterclockwise rotates 90 degree for opening the valve after being driven departing from the valve seat by the valve stem when the valve stem is lifting. The ball is driven clockwise rotating 90 degree by the valve stem when the valve stem is descending and then the ball presses the valve for closing the valve. Disadvantageous of this valve is that the guiding groove occupies much space and the rotation angle is large as the valve stem has a long s-shape guiding groove so that the valve stem requires spiraling up or down when the valve is closed.
Chinese Patent Application No. 99124192.4 disclosed a rotary disc-shaped double-track “rotating” and “expanding and narrowing” opening and closing valve structure, which consists of a fixed disk, a rotating disk and a position limiting pin. When an external force drives the valve stem along with the rotating disk, the position limiting pin is actuated and clockwise rotates along the trajectory of the “circle” track on the fixed disk. When the position limiting pin rotates to a “straight line” track connecting to the “circle” track, the rotating disk continues to clockwise rotating. The position limiting pin is expanded toward the periphery of the fixed disk along the “straight line” of the fixed disk under the force of the “expanding and narrowing” track on the rotating disk, when the position limiting pin together with the valve sealing structure moves towards a valve seat to close the valve. The position limiting pin together with the valve sealing structure firstly narrows toward the center of the fixed disk along the “straight line” track of the fixed disk and secondly counterclockwise rotates along the “circle” track of the fixed disk so as to open the valve under the force of the “expanding and narrowing” track on the rotating disk, when the valve stem together with the rotating disk counterclockwise rotates. The disadvantages of this patent is that it employs “circle connecting straight line” track which requires high precision, complex processing technology and the valve cartridge is a assembly of ball so that it is difficult to obtain a balanced preload, resulting in damage of valve cartridge and shorten life of the valve.
Chinese patent 200620105067 disclose a track-type plug valve including a valve body, a valve cover, an operating member, a valve stem, a valve seat, a valve plug which forms a conical sealing pair of element with the valve seat, and track structure, which consists of a track ring with two guiding grooves mounted on the neck of the valve plug and dual pin plate with two guiding pins inserting in the two guiding grooves. The track structure further comprises a locknut for adjusting a position of the track ring and an adjusting ring. Disadvantage of this patent is that a transmission device has a complex structure, occupies much of space, and involves a lot of components, and the assembly process is complex. Furthermore, as it has the valve plug which with a conical sealing pair of element, the locknut for adjusting a position of the track ring and the adjusting ring, it requires multiple adjustment, resulting in complicated operation.